A number of surgical techniques and approaches involve establishing a working channel to gain access to a target site of surgical interest. Depending on the anatomical location of the surgical target site and the approach, the instruments required for the surgery may pass near nervous system structures, which in turn can be damaged if contacted by the surgical instruments. Examples of different surgical fields where this may be an issue include spinal, urological, vascular, and cardiothoracic surgery.
Currently, there are systems that attempt to provide neurophysiological monitoring to help reduce the risk of nerve or other damage by creating a stimulating current from a surgical device. This current, in turn, stimulates any nerves that are in close proximity to the surgical device. If these nerves have a motor component, this stimulating current then activates the nerve and the impulse travels downstream to a muscle group and activates that muscle. Surface or needle electrodes that are in or near the muscle that is activated can pick up the electrical activity generated by the muscle twitch. This process of recording electrical activity generated by contracting muscles is called electromyography (EMG).
During some types of minimally invasive spinal surgery, dissection and dilation through the iliopsoas muscle places the lumbosacral plexus at risk for mechanical injury, particularly at the L4-L5 level, as the position of the nerve root is more anterior compared with the upper lumbar levels. Serious approach related complications from the transpsoas technique occur frequently and are likely underreported. Literature review suggests several case reports with adverse outcomes resulting in transient or permanent motor deficits as a result of nerve damage. This is occurring even with the current systems of neurophysiological monitoring and improved systems would certainly be beneficial.
Therefore, apparatus and methods for guiding and/or manipulating surgical instruments relative to nervous tissue would be useful.